Browsing by Author "S.T. NKALUBO"

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DEVELOPMENT OF INTERMITTENT DROUGHT STRESS TOLERANT COMMON BEAN GENOTYPES IN UGANDA
(African Crop Science Society, 2014-11-09) W. AMONGI; S.T. NKALUBO; M. OCHWO-SSEMAKULA; P.T. GIBSON; R. EDEMA
Common bean (Phaseolus vulgaris L.) varieties that are high yielding and drought-tolerant are crucial in coping with the effects of drought, that is prevalent among small scale producers living in Uganda. The objective of this study was to assess the level of drought tolerance in bean genotypes to be used for the initial development of drought-tolerant genotypes in Uganda. Three local genotypes and five exotic drought-tolerant lines were phenotyped under well-watered and drought-stress conditions. Drought tolerant genotypes were selected basing on high value for the geometric mean for seed yield and low drought susceptibility indices. The exotic lines, SEN 98, SCR48 and SEN 99, emerged superior in these attributes, and in pod partitioning index (PPI) and pod harvest index (PHI). Thus, these genotypes could be useful sources of genes for drought tolerance in the bean breeding programme in Uganda. The local genotype, NABE 15 was similar to the three promising materials for PPI and PHI. Pods per plant and seed weight were the yield components most affected by drought, with reductions of 82 and 78 %, respectively, for SEN 98.
Genetic progress achieved in bean breeding in Uganda.
(African Crop Science Journal, 2022-12-18) A. MUKAYIRANGA; P. RUBAIHAYO; P.T. GIBSON; R. EDEMA; S.T. NKALUBO; Z.A. CHITEKA; A. RUTAYISIRE
Several cultivars of common bean (Phaseolus vulgaris L.) have been released in Uganda over a period of five decades, but the genetic gain to selection in respect of yield and agronomic characteristics has not been determined. This study was conducted to estimate the gain in selection over the 1960 - 2016 period, of common bean breeding in Uganda. Twenty nine bush and eleven climbing type cultivars were evaluated for yield and yield components, in three locations, during 2017B and 2018A cropping seasons. The study was carried out at the National Crop Resources Research Institute (NaCCRI), Nakabango Research Institute in central and Kwachwekano Zonal Agriculture Research Institute in southwestern Uganda. The design used was a randomised complete blocks with three replicates for the climbing types; and a 3x10 Alpha lattice design with three replicates for bush types. Significant differences (P<0.001) were recorded among cultivars for most traits in both bush and climbers, except seed number per pod (NSP). The range of genetic gain in grain yield was between 1,505 to 2,418 kg ha-1 for bush type cultivars, and 1,641 to 2,687 kg ha-1 for the climbing types. Yield has increased by16.3 and 26.3 kg ha-1 per year for bush and climbers, respectively; with a relative gain of 1.27%/year for bush types and 1.54%/year for the climbing types. Biomass yield and harvest index explained most of the variation in grain yield and number of pods per plant in climbing types. Among climbing types, biomass yield was significantly and positively correlated with grain yield per plant and grain yield per ha (P<0.05, and r= 0.87) and with grain yield per ha (P<0.01 r = 0.98) for bush types, biomass yield was significantly and positively correlated with grain yield per plant (P<0.05, and r= 0.59) and with grain yield per ha (P<0.01 r = 0.80) and harvest index (P<0.5 r = 0.80).
SUSCEPTIBILITY TO BRUCHIDS AMONG COMMON BEANS IN UGANDA
(African Crop Science Society, 2016-10-02) J.A. EBINU; V. NSABIYERA; M. OTIM; S.T. NKALUBO; M.UGEN; A.J. AGONA; H.L. TALWANA
The bean bruchids, Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae), are cosmopolitan pests of stored dry common beans (Phaseolus vulgaris L.), causing damage through reduction of grain quality and seed germination. Biological resistance to these bruchids was definitively established in non- cultivated bean accessions, and has been introgressed into a range of drybean market classes. However, existing resistance to bruchids in Uganda’s common bean germplasm has not been systematically studied. In this study, 45 bean genotypes from the National Bean-Breeding Programme (25 genotypes) and agroecologically diverse bean growing areas in Uganda (20 genotypes), were evaluated for postharvest bruchid resistance. None of the evaluated bean genotypes expressed resistance to either bruchid species, with all the 45 bean genotypes supporting bruchid development, reproduction and feeding. All genotypes were severely damaged by bruchids feeding, resulting in significant (P<0.05) reduction of seed germination. Reduction in seed germination was related to the number of emergence holes and seed size; small bean seeds damaged by up to 2 bruchid emergence holes had a 7.1% reduction in germination, while large bean seeds with a similar number of emergence holes showed a 25% reduction in germination. Whereas this study further confirms bruchids as important storage pests of beans causing direct loss through consumption of the seed and indirect loss through viability deterioration, the resistance to bruchids in the evaluated range of Uganda’s dry bean germplasm is inadequate for direct exploitation in a breeding programme.